Storage phosphor imaging systems are known. In one such system, a storage phosphor is exposed to an x-ray image of an object, such as a body part of a patient, to record a latent x-ray image in the storage phosphor. The latent x-ray image is read out by stimulating the storage phosphor with stimulating radiation. Upon stimulation, the storage phosphor releases emitted radiation of a particular wavelength. To produce a signal useful in electronic image processing, the storage phosphor is scanned, for example, by a laser beam deflected by an oscillating or rotating scanning mirror or by a rotating polygon. The emitted radiation from the storage phosphor is reflected by a collector and detected by a photodetector, such as a photomultiplier, to produce an electronic x-ray image signal. The x-ray image signal can then be viewed as a visual image produced by a softcopy display device, such as a CRT or LCD display, or a hardcopy display device, such as a x-ray film printer (laser printer, CRT printer, thermal printer). U.S. Pat. No. Re. 31,847, issued Mar. 12, 1985, inventor Luckey discloses a storage phosphor system. The reader is often referred to as a computed radiography (CR) reader.
The storage phosphor can be disposed on a medium. Such a medium can be flexible, semi-flexible, semi-rigid, or rigid, and can be configured as a sheet or other substantially planar arrangement.
When the storage phosphor is being processed/scanned/read/exposed by the storage phosphor processor/reader, the position of the storage phosphor can be controlled so as to not introduce any artifacts in the processed image.
During scanning, the laser beam is scanned in a scanline over the surface of a storage phosphor screen by a reciprocating galvanometer mirror or polygon rotating mirror in a fast scan direction while the screen is transported under the scanline in a slow scan direction. The reflected light is collected by a light collector and reflected into photomultiplier tubes (PMTs). The light levels are collected by the PMT's and transmitted to the reader electronics were the image is processed.
Prior to operation, the scanline is adjusted to a particular position where the laser beam is not obstructed and the phosphor screen is well controlled for position height. The alignment of the scanline for rotation and translation to a required position is known, for example, as disclosed in U.S. Ser. No. 10/742,222, titled SCANLINE ALIGNMENT SENSORS, by Urbon et al., commonly assigned and incorporated herein by reference.
To maximize the reflected light collected by the light collector, the input opening (e.g., slot) provided for the scanline to enter the light collector must be minimized and the light collector input opening needs to be aligned to the scanline. That is, the position of the scanline as it passes through the light collector is important to promote maximum light transmission by the laser while maintaining a minimum scanline slot opening to maximize the reflected light collected by the collector. Accordingly, there exists a need for an apparatus and method to correctly and accurately position the scanline so as to maximize the light transmission by the laser.
Existing manual methods can be cumbersome and require particular safety precautions. For example, positioning of the scanline can be accomplished visually by an operator observing the scanline while adjusting two axes of a fold mirror, placed in the path of the scanline, as the scanline strikes a tool placed in the scanline path near the entrance of the collector. This technique requires safety hardware and procedures to be followed to ensure laser safety in the presence of the exposed laser beam. Yet, the process can result in significant residual misalignment since the adjustment process is subjective, operator dependent, and the tool is not able to directly interface with the limiting features of the opening.
Accordingly, a need continues to exist for an apparatus and method for correctly and accurately position the scanline so as to maximize the light transmission by the laser while overcoming the problems of existing methods noted above.